There is no longer any strict definition regarding what is considered to be "working at heights"; the onus is now on both workers and supervisors to minimise the likelihood of a fall from any height.
In Western Australia, it was previously the case that a person was considered to be working at heights in accordance with WA Occupational Safety and Health Regulations 1996, Part 3, Division 5, 3.55 and the WorkSafe WA code of Practice: The Prevention of Falls at Workplaces.
Regardless, certain obligations remain. Firstly, contractors must supply a Job Safety Analysis (JSA) to the responsible officer before any works start.
Further, all work at heights that requires use of a harness must be performed by someone with a current Work Safely at Heights certificate, and two or more people must be present. Scaffolds and scaffolding equipment must meet AS/NZS 1576 and the WA Occupational Safety & Health Regulation 1996 / Section 3.72 Inspection and marking of certain scaffolds. As well:
All ladders must comply with relevant Australian Standards and be positioned and used as described in the WorkSafe WA Code of Practice: The Prevention of Falls at Workplaces.
All necessary precautions must be taken by the contractor to protect people and property from falling objects, debris and tools before overhead work starts and at all times during work.